Heretofore, some 3-(substituted)phenyl-2-pyridone derivatives have been known. However, no more than a few compounds have been known with respect to 3-(substituted)phenyl-6-(substituted)alkyl-2-pyridone derivatives, which represent the characteristic of the compounds of the present invention. For example, the specification of JP-B-46-30190 discloses 3-(4-chlorophenyl)-6-methyl-2-pyridone. Further, U.S. Pat. No. 3,720,768 discloses 3-phenyl-6-ethyl-2-pyridone. However, either specification discloses nothing about herbicidal activities. On the other hand, some 3-(substituted)phenyl-4-pyridone derivatives have been known. However, no more than a few compound have been known with respect to 3-(substituted)phenyl-6-(substituted)alkyl-4-pyridone derivatives, which represent the characteristic of the compounds of the present invention. For example, Chemical Abstract vol. 76, No. 140407, discloses 3-phenyl-6-methyl-4-pyridone, but discloses nothing about the herbicidal activities. Further, the specification of JP-A-62-167708 discloses a 3-(substituted)phenyl-6-(substituted)alkyl-4-pyridone derivative having a carbamoyl group at the 5-position, and a herbicidal activity is also disclosed. However, it is different from the compounds of the present invention.
In recent years, a herbicide is strongly desired which has selective activities to kill only weeds without giving adverse effects to crop plants even when it is applied to the crop plants and weeds simultaneously. Further, it is desired to develop an agent whereby complete effects can be obtained at a low dose, in order to prevent the agent from remaining excessively in the environment.
To solve the above problems, the present inventors have synthesized many pyridone derivatives and conducted various studies on their usefulness. As a result, it has been found that certain pyridone derivatives have excellent herbicidal activities and selectivity to solve the above problems, and the present invention has been accomplished.